#更多更多的练习，文本处理
def break_words(stuff):
    """This function will break up words for us."""
    words=stuff.split(' ')
    return words

def sort_words(words):
    """Sorts the words."""
    return sorted(words)

def print_first_word(words):
    """Prints the first word after popping it off."""
    word=words.pop(0)
    print(word)

def print_last_word(words):
    """Prints the last word after popping it off."""
    word=words.pop(-1)
    print(word)

def sort_sentence(sentence):
    """Takes in a full sentence and returns the sorted words."""
    words=break_words(sentence)
    return sort_words(words)

def print_first_and_last(sentence):
    """Print the first and last words of the sentence."""
    words=break_words(sentence)
    print_first_word(words)
    print_last_word(words)

def print_first_and_last_sorted(sentence):
    """Sorts the words then prints the first and last one."""
    words=sort_sentence(sentence)
    print_first_word(words)
    print_last_word(words)


#unboundlocalerror:local variable 'word' reeferenced before assignment
#局部变量赋值前被引用，原因是局部变量与全局变量同名，三引号为帮助提示内容
